With the development of integrated circuit technology, the feature sizes of semiconductor devices are getting smaller and smaller. In order to reduce parasitic capacitance between metal interconnect lines, a low-k dielectric material is gradually used instead of silicon dioxide in the interconnect structure. A porous ultra-low-k material can further reduce the dielectric constant of a dielectric material in the interconnect structure, so that porous ultra-low-k materials are used in interconnect structures in smaller-sized devices.